1. Field of the Invention
The present invention relates to a disk-shaped substrate manufacturing method. As the disk-shaped substrate, a glass substrate for magnetic recording medium is exemplified.
2. Description of the Related Art
In recent years, the manufacture of disk substrates as disk-shaped substrates has become activated, under increased demands as recording media. As a magnetic disk substrate that is one of the disk substrates, an aluminum substrate and a glass substrate are used widely. The aluminum substrate is characterized by its high processability and low cost, meanwhile the glass substrate is characterized by its excellent strength, surface smoothness and flatness. In particular, requirements for compact size and high density of disk substrates recently have become extremely high, and the glass substrate of which surface roughness is small and that enables high density has attracted a lot of attention.
In the manufacture of such a magnetic disk substrate, it is important to enhance smoothness and flatness of the substrate by optimizing grinding and polishing conditions in grinding and polishing processes. In the recent years, the environment in the manufacturing process has been considered as an important factor as well as optimization of the grinding and polishing conditions. Among related arts described in official gazettes, there is an art of performing the final polishing on a substrate in a clean room while washing the substrate with a washing liquid. This method is employed in order to avoid a quality problem which might be caused if dust in the atmosphere attaches to the surface of the substrate after the final polishing of the substrate (for example, see Patent Document 1).
There is a different art described in an official gazette of performing a grinding process in the atmosphere, and performing a polishing process and the following processes in a clean room (dust-free room) with an attempt to prevent particles floating in the air from attaching to the substrate in the polishing process (for example, see Patent Document 2).
[Patent Document 1]    Japanese Patent Application Laid Open Publication No. 9-288820
[Patent Document 2]    Japanese Patent Application Laid Open Publication No.
Heretofore, there has been a challenge to prevent attachment of particles floating in the atmosphere to a substrate. In related arts, such a challenge is achieved by conducting processes, in which attachment of particles may be problematic, in a clean room. However, if all the processes in which attachment of particles is problematic are carried out in a clean room, the construction of a clean room as well as operation and maintenance of the facility requires an enormous amount of cost. Thus, the initial cost (initial investment cost) is increased, and thereby the manufacturing cost is increased. Especially, manufacturing of the magnetic disk substrate, which employs a cutting-edge technology, has a high rate of product turnover; thus, the cost spent on manufacturing facilities is an extremely influential factor in the product.
In the meantime, there is a variation in how particles should be removed among the manufacturing processes in the manufacturing of the magnetic disk substrate. For example, in the grinding process and the early polishing process, there is almost no adverse effect on the final product even if a relatively simple particle removal operation is performed. In contrast, if no step is taken at all for removal of particles, for example, particles floating in the atmosphere may attach to the surface of a magnetic disk substrate, and, for example, particles come to be mixed in a polishing liquid, thereby degrading the smoothness of the surface of the substrate. For these reasons, it has been strongly desired that particles are removed efficiently in a simple facility, without having to make a large facility investment such as a clean room.
The present invention has an object to establish a favorable environment for removing dust with a low facility cost and to manufacture a high-precision disk-shaped substrate in such a favorable dust removal environment.